The insulin effect on the regulation of renal sugar transport and metabolism will be studied: 1. The distribution of key enzymes of carbohydrate metabolism (e.g., hexokinases, glucose-6-phosphatase, and fructose-l,6-diphosphatase, phospho-enol-pyruvate carboxykinase and pyruvate dehydrogenase will be determined in the renal cortex of normal, hypoinsulinemic (streptozotocin-treated) and hyperinsulinemic (obese, Zucker) rats. The data will be correlated with results of studies on the insulin effect on sugar transport at the antiluminal cell face of renal cortical tubules, using the selective entry of the non-metabolizable 3-O-methyl-D-glucose as a marker. 2. Active sugar transport (and gluconeogenesis), and the effect of insulin and other agents involved in the regulation of renal sugar transport and metabolism will be investigated in the LLC-PKl line of renal epithelial cells grown in vitro. 3. The mechanism of active fructose transport will be determined using vesicles of microvilli from the renal cortex of newborn piglets and lambs; fructose is the dominant plasma sugar in newborns of these mammal species, and its level is not affected by insulin. 4. The mechanism of the novel phenomenon of sugar secretion in the kidney (and intestine) of the flounder (Pseudopleuronectes americanus) will be elucidated.